Many salad dressings are composed of a mixture of ingredients such as oil and vinegar which tend to separate from one another when sitting at rest. Consequently, such dressings must be constantly stirred or shaken in order to mix them prior to pouring them onto a salad.
While it is possible to shake a cruet or other such container to mix a dressing, the results are uneven and the shaking or stirring process can create a mess. In addition, if the dressing is poured directly from the bottle without shaking, the result is an application of a dressing that is imbalanced and dominated by the lightest ingredient that has risen to the top. Despite this well-known and long-standing problem, current salad dressing containers remain the same and fail to address the issue.